The award has come at a time when the tensions between the Islamic republic and the US are at its peak over Iran`s nuclear programme.
Directed by Asghar Farhadi, the film also won the best foreign film at the Golden Globes. Farhadi was nominated for a best screenplay Oscar. "At this time, many Iranians all over the world are watching us and I imagine them to be very happy," Farhadi said, reading from prepared remarks on a piece of paper on Sunday night.
"They are happy not just because of an important award or a film or a filmmaker, but because at the time when talk of war, intimidation and aggression is exchanged between politicians, the name of their country, Iran, is spoken here through her glorious culture, her rich and ancient culture that has been hidden under the heavy dust of politics."
"I proudly offer this award to the people of my country, a people who respect all cultures and civilizations and despise hostility and resentment. Thank you so much," he added.
The film begins with two couple`s seeking divorce, which eventually goes onto explore themes of honour, love, lies and deceit. The only other Iranian movie nominated at the Oscars was 1997`s "Children of Heaven" which lost to "Life Is Beautiful" from Italy.
The other films competing were Michael R Roskam`s "Bullhead" from Belgium; Philippe Falardeau`s "Monsieur Lazhar" from Canada; Joseph Cedar`s "Footnote" from Israel; and Agnieszka Holland`s "In Darkness" from Poland.